CVE-2023-4612
📋 TL;DR
CVE-2023-4612 is an authentication bypass vulnerability in Apereo CAS that allows attackers to circumvent Multi-Factor Authentication by manipulating the remote address in HTTP requests. This affects all CAS deployments through version 7.0.0-RC7. Organizations using vulnerable CAS versions for authentication are at risk.
💻 Affected Systems
- Apereo CAS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete authentication bypass allowing unauthorized access to protected systems and data, potentially leading to account takeover, data exfiltration, and privilege escalation.
Likely Case
Attackers bypass MFA requirements to gain unauthorized access to applications protected by CAS, potentially accessing sensitive information or performing unauthorized actions.
If Mitigated
With proper network segmentation and additional authentication layers, impact is limited to the CAS application layer only.
🎯 Exploit Status
Exploitation requires manipulating HTTP request headers to spoof remote addresses, which is relatively straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: None available
Vendor Advisory: None - vendor does not treat this as a vulnerability
Restart Required: No
Instructions:
No official patch available. Consider upgrading to newer versions if they address the issue, but vendor has not confirmed fixes.
🔧 Temporary Workarounds
Implement Reverse Proxy IP Validation
allConfigure reverse proxies to strip or validate X-Forwarded-For headers and ensure proper IP address validation
# Configure nginx: proxy_set_header X-Real-IP $remote_addr;
# Configure Apache: RequestHeader set X-Forwarded-For "expr=%{REMOTE_ADDR}"
Implement Additional Authentication Layer
allAdd secondary authentication checks independent of remote address validation
🧯 If You Can't Patch
- Implement network-level controls to restrict access to CAS servers
- Deploy Web Application Firewall (WAF) rules to detect and block suspicious authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check CAS version with: java -jar cas.war --version or review deployment configuration files for version informationCheck Version:
java -jar cas.war --version 2>&1 | grep -i versionVerify Fix Applied:
Test authentication with manipulated X-Forwarded-For headers to verify MFA cannot be bypassed📡 Detection & Monitoring
Log Indicators:
- Multiple authentication attempts from same user with different IP addresses
- Successful authentications with suspicious X-Forwarded-For header patterns
Network Indicators:
- HTTP requests with manipulated X-Forwarded-For headers during authentication flows
SIEM Query:
source="cas.log" AND ("authentication success" OR "MFA bypass") AND ("X-Forwarded-For" OR "remote_addr")